Endotracheal cuff and technique for using the same

ABSTRACT

An inflatable balloon cuff may be adapted to seal a patient&#39;s trachea when associated with an endotracheal tube. Configurations of these cuffs that include tapered regions with certain characteristics, such as cuff wall diameter and thickness, may provide improved sealing of the trachea.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/472,733filed Jun. 22, 2006, entitled “Endotracheal Cuff and Technique for Usingthe Same” in the name of Donald S. Nelson et al., and assigned toNellcor Puritan Bennett LLC, which is incorporated by reference hereinin its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to medical devices, and more particularly,to airway products, such as tracheal tubes and cuffs.

2. Description of the Related Art

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present invention,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentinvention. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

In the course of treating a patient, a tube or other medical device maybe used to control the flow of air, food, fluids, or other substancesinto the patient. For example, medical devices such as tracheal tubesmay be used to control the flow of one or more substances into or out ofa patient. In many instances it is desirable to provide a seal betweenthe outside of the tube or device and the interior of the passage inwhich the tube or device is inserted. In this way, substances can onlyflow through the passage via the tube or other medical device, allowinga medical practitioner to maintain control over the type and amount ofsubstances flowing into and out of the patient.

For example, tracheal tubes may be used to control the flow of air orother gases through a patient's trachea. Such tracheal tubes may includeendotracheal (ET) tubes, tracheostomy tubes, or transtracheal tubes. Toseal these types of tracheal tubes, an inflatable cuff may be associatedwith these tubes. When inflated, the cuff generally expands into thesurrounding trachea to seal the tracheal passage around the tube.

However, to fit a range of trachea anatomies and to provide low intracuff pressure, cuff diameters are usually about one and a half times thediameter of the average trachea. Therefore, when inserted in anaverage-sized trachea, such a cuff is unable to fully expand and willfold in on itself within the trachea. These folds may serve as leakpaths that allow mucosal secretions to flow past the cuff and enter thelung.

SUMMARY

Certain aspects commensurate in scope with the originally claimedinvention are set forth below. It should be understood that theseaspects are presented merely to provide the reader with a brief summaryof certain forms the invention might take and that these aspects are notintended to limit the scope of the invention. Indeed, the invention mayencompass a variety of aspects that may not be set forth below.

There is provided an inflatable balloon cuff that includes a proximalopening and a distal opening in a wall of the balloon cuff; and atapered section along at least 50% of the length along an axis of theinflated balloon cuff, wherein the tapered section comprises a taperangle of at least 15 degrees, measured as an included angle of at leasta portion of the tapered section and an imaginary axis connecting theproximal opening and the distal opening.

There is also provided a method of manufacturing an inflatable ballooncuff that includes providing a proximal opening and a distal opening ina wall of the balloon cuff; and providing a tapered section along atleast 50% of the length along an axis of the inflated balloon cuff,wherein the tapered section comprises a taper angle of at least 15degrees, measured as an included angle of at least a portion of thetapered section and an imaginary axis connecting the proximal openingand the distal opening.

There is also provided an inflatable balloon cuff that includes atapered section, wherein a balloon wall of the tapered section is ofcontinuously varying thickness along the tapered section such that theballoon wall at the widest point of the tapered section is thinner thanthe balloon wall at the narrowest point of the tapered section.

There is also provided a method of manufacturing an inflatable ballooncuff that includes providing an inflatable balloon cuff having a taperedsection, wherein a balloon wall of the tapered section is ofcontinuously varying thickness along the tapered section such that theballoon wall at the widest point of the tapered section is thinner thanthe balloon wall at the narrowest point of the tapered section.

There is also provided an inflatable balloon cuff that includes atapered section, wherein at least a portion of the tapered section isadapted to form a wrinkle-free band against a patient's tracheal wallwhen inflated.

There is also provided a method of manufacturing an inflatable ballooncuff that includes providing an inflatable balloon cuff having a taperedsection, wherein at least a portion of the tapered section is adapted toform a wrinkle-free band against a patient's tracheal wall wheninflated.

There is also provided an inflatable balloon cuff that includes atapered section comprising at least a portion of the balloon cuff,wherein at least a portion of the balloon walls in the tapered sectionare less than 60 microns in thickness.

There is also provided a method of manufacturing an inflatable ballooncuff that includes providing an inflatable balloon cuff having a taperedsection comprising at least a portion of the balloon cuff, wherein atleast a portion of the balloon walls in the tapered section are lessthan 60 microns in thickness.

There is also provided an inflatable balloon cuff that includes aproximal opening and a distal opening in a wall of the balloon cuff; afirst tapered section along an imaginary axis connecting the proximalopening and the distal opening of the inflated balloon cuff; and asecond tapered section along the imaginary axis connecting the proximalopening and the distal opening.

There is also provided an inflatable balloon cuff that includes atapered section, wherein a balloon wall of the tapered section is ofconstant along the tapered section.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the invention may become apparent upon reading thefollowing detailed description and upon reference to the drawings inwhich:

FIG. 1 illustrates an endotracheal tube with an inflatable balloon cuffin accordance with aspects of the present technique;

FIG. 2 illustrates the inflatable balloon cuff of the present techniquesinserted into a patient's trachea;

FIG. 3 illustrates three different regions of the balloon cuff of thepresent techniques after insertion into a patient's trachea;

FIG. 4 is a top view of the wrinkled region of the balloon cuff of FIG.3;

FIG. 5 is a top view of the wrinkleless band region of the balloon cuffof FIG. 3;

FIG. 6 is a top view of the minimal contact region of the balloon cuffof FIG. 3;

FIG. 7 illustrates an alternate configuration of the balloon cuff of thepresent techniques in which the cuff tapers towards the proximal end ofthe conduit;

FIG. 8 illustrates an alternate configuration of the balloon cuff of thepresent techniques having a generally hourglass configuration;

FIG. 9 illustrates an alternate configuration of the balloon cuff of thepresent techniques having a generally diamond-like configuration;

FIG. 10 is a flowchart depicting a blowmolding method of manufacturing aballoon cuff of the present techniques; and

FIG. 11 illustrates a balloon cuff of the present techniques with anantimicrobial layer.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, not all features of an actual implementation are describedin the specification. It should be appreciated that in the developmentof any such actual implementation, as in any engineering or designproject, numerous implementation-specific decisions must be made toachieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

It is desirable to provide a medical balloon, such as an endotrachealcuff or other medical device, which may substantially seal the passagein which the cuff is inserted so that mechanical ventilation can be usedto introduce air, oxygen, or medications into the lungs. In accordancewith some aspects of the present technique, a medical balloon with atapered shape is provided that is adapted to be used with anendotracheal tube or device.

The tapered balloon cuffs provided herein may provide advantages over atypical cuff. A typical inflatable cuff generally assumes a cylindricalor barrel shape when inflated that may include short tapered orpartially tapered sections designed to connect the ends of the cuff to anarrower object, such as an endotracheal tube. Thus, a generallycylindrical cuff has a constant diameter along most of its length whenfully inflated. This diameter is typically larger than the size of thetracheal passage. Therefore, when a typical cylindrical cuff is insertedinto a patient's trachea and inflated, the cuff walls of the cylinderare unable to inflate to their maximum diameter and may fold in onthemselves, which may cause wrinkles and leak paths to form.

A tapered cuff provides an improved seal against a patient's passage.Tapered cuffs include at least one section with a tapered shape. Thetapered section includes a section that comes into direct contact with apatient's trachea. It should be understood that, in certain embodiments,the tapered section may be only a portion of the entire cuff. Thetapered shape of the cuffs as provided herein results in the cuffdisplaying a range of inflated cuff diameters along the axis of thepatient's passage. This range of cuff diameters results in at least oneregion along the inflated cuff that is substantially equal in diameterto a patient's trachea. The portion of the tapered cuff with a diameterthat is substantially sized to the diameter of the trachea provides arelatively higher quality seal against the trachea that is substantiallywrinkle-free.

The tapered shape of the cuffs as provided herein may be characterizedby the cuff diameters at both ends of the taper. For example, thetapered shape may be described by providing the cuff diameter at thewidest point of the taper as well as the cuff diameter at a narrowerpoint. It should be understood that cuff diameters may be measured whenthe cuff is fully inflated while not inserted in a patient trachea alongan axis that is substantially orthogonal to the axis of the endotrachealtube. A cuff diameter may be measured from cuff wall to cuff wall,either exterior wall to exterior wall or interior wall to interior wall.In certain embodiments, the taper may range from two times the size ofan average trachea at the widest point to half the size of the averagetrachea or smaller at the narrowest part of the taper. It should beunderstood that an average trachea size may be an adult male or femaleaverage size that is based on height and weight, or a child averagesize. For example, an adult trachea may range in size from 14 mm to 27mm, with the average being around 20 mm. Women typically use a size 7.0to 7.5 endotracheal tube, while men may use a size 7.5 to 8.0endotracheal tube. The size of the tube typically refers to the insidediameter of the main airway tube. In specific embodiments, the taperedregion may narrow from a widest cuff diameter of 1.355 inches to anarrower diameter of 0.65 inches or smaller. It is envisioned that asingle cuff may be designed to accommodate a wide variety of trachealsizes along a single taper. Thus, a further advantage of a tapered cuffmay be its adaptability to patients of a variety of sizes. In oneembodiment, certain smaller diameters at the narrow end of the cufftaper are associated with increased sealing performance. For example,certain smaller diameters at the narrow end may maintain the sealingband of the cuff around the trachea even though the tube itself may notbe centered in the trachea. Due to the curvature typically built intotracheal tubes for ease of insertion and patient comfort, the tube doesnot necessarily stay centered in the trachea. By having smallerdiameters at the narrow end, it is possible to maintain the benefits ofthe tapered shape even when the tube is not symmetrically located withinthe trachea. Thus, in certain embodiments it may be desirable to havecuff diameters less than 0.65 inches or less than 0.60 inches at thenarrow end of the cuff. The cuff diameters may be even smaller forsmaller patients, such as pediatric patients, and in certain embodimentsmay only be limited by the outer diameter of the tubing that issufficient to achieve acceptable ventilation of the patient.

In other embodiments, the tapered region of the tapered cuff may becharacterized by the slope or angle of the taper, which is the includedangle of the tapering cuff wall and the axis of an attached endotrachealtube. For example, the angle of the taper may include a tapering angleof at least 15 degrees, at least 20 degrees, or at least 25 degrees. Ina specific embodiment, the angle of the taper may be between 17 and 20degrees. Providing tapering angles greater than 15 degrees generallyindicates a greater variance between the widest point and the narrowerpoint of the taper. Further, the tapered region of the tapered cuff maybe characterized in certain embodiments by the rate of tapering from thewidest point of the taper to a narrower point. A cuff may exhibit acontinuous rate of tapering, or a linear tapering, from a wider diameterto a narrower diameter. Cuffs with linear tapering may be less costly tomanufacture. In other embodiments, the taper may have a nonlinear rateof tapering. For example, it may be advantageous to provide stepwisetapering along the cuff, whereby a certain cuff diameter is maintainedfor 5-10 mm along the length of the taper. The taper may also becharacterized by a monotonically decreasing function, such as ahyperbola. Additionally, a taper may be characterized by its lengthalong the axis of an endotracheal tube. For example, a taper may bealong at least 30%, at least 40%, at least 50%, at least 75%, or atleast 95% of the length of the cuff along a specific axis.

Tapered medical cuffs as provided herein may be used in conjunction withany suitable medical device. In certain embodiments, the tapered cuffsas provided herein may be used in conjunction with a catheter, a stent,a feeding tube, an intravenous tube, an endotracheal tube, atracheostomy tube, a circuit, an airway accessory, a connector, anadapter, a filter, a humidifier, a nebulizer, or a prosthetic, invarious embodiments.

An example of a tapered cuff used in conjunction with a medical deviceis a cuffed endotracheal tube 10, depicted in FIG. 1. The cuffedendotracheal tube 10 includes an inflatable tapered cuff 12 that may beinflated to form a seal against the trachea wall 28 (see FIG. 2). Thetapered cuff is disposed on an endotracheal tube 16 that is suitablysized and shaped to be inserted into a patient and allow the passage ofair through the endotracheal tube 16. Typically, the cuff is disposed,adhesively or otherwise, towards the distal end 17 of the endotrachealtube 16. The tapered cuff 12 may be inflated and deflated via a lumen 14in communication with the tapered cuff 12, typically through a hole ornotch in the lumen 14. The tapered cuff 12 may generally have anamorphous, or irregular, shape in the uninflated state and may assumethe tapered shape when inflated. The tapered cuff 12 has a proximalopening 20 and a distal opening 22 formed in the cuff walls 24 sized toaccommodate the endotracheal tube 16. The proximal opening 20, locatedcloser to the “machine end” of the tube 16, and a distal opening 22,located closer to the “patient end” of the tube 16, are typically usedto mount the cuff 12 to the tube 16.

The tapered cuff 12 may be formed from materials having suitablemechanical properties (such as puncture resistance, pin hole resistance,tensile strength), chemical properties (such as forming a suitable bondto the tube 16), and biocompatibility. In one embodiment, the walls ofthe inflatable cuff 12 are made of a polyurethane having suitablemechanical and chemical properties. An example of a suitablepolyurethane is Dow Pellethane® 2363-90A. In another embodiment, thewalls of the inflatable cuff 12 are made of a suitable polyvinylchloride (PVC). Other suitable materials include polypropylene,polyethylene teraphthalate (PETP), low-density polyethylene (LDPE),silicone, neoprene, polyisoprene, or polyurethane (PU).

FIG. 2 shows the exemplary cuffed endotracheal tube 10 inserted into apatient's trachea. The tapered cuff 12 is inflated to form a sealagainst the tracheal walls 28 and may prevent secretions 30 or otherdetritus from passing through the trachea into the lungs. The taperedcuff 12 assumes a partially tapered shape when inserted in the patient'strachea, as described in more detail in FIGS. 3-6.

As depicted in FIG. 3, the tapered shape of the cuff 12 may result indifferent regions of the tapered cuff 12 interacting with the trachea ina variety of manners. One portion of the tapered cuff 12 includes cuffwalls with fully inflated diameters larger than the diameter of thetracheal passage 38. As the cuff walls of this region inflate within thetrachea, they encounter the tracheal walls 28 and are prevented fromassuming their fully inflated diameters, as is normally the case withhigh volume low pressure cuffs. Thus, the tapered cuff in this regionmay be partially flattened against the tracheal walls 28 to create awrinkled region 32 of the cuff (see FIG. 4). A portion of the taperedcuff 12 that includes cuff walls with diameters substantially equal tothe diameter of the tracheal passage 38 may form a wrinkle-free band 34(see FIG. 5) against the tracheal walls 26, as in this region of thetapered cuff 12, the cuff walls assume their fully inflated diameters.The region 36 of the tapered cuff 12 with a diameter smaller than thepassage may form a minimal contact or no contact region 36 (see FIG. 6)with the tracheal walls.

FIG. 4 depicts a top view of cross-section through the wrinkled region32 of an inserted tapered cuff 12. As depicted, the cuff walls 24 may beunable to inflate to their fully inflated diameters in the trachealpassage. In order to fit into the passage, the flexible cuff walls 24 ofthe tapered cuff 12 fold in on each other and may form multiple wrinkles40. It should be understood that, depending on how a cuffed endotrachealtube 10 is inserted into the trachea, the tapered cuff 12 may not becompletely centered within the tracheal passage.

FIG. 5 depicts a top view of a cross-section through the region of thesubstantially wrinkle-free band 34 of the tapered cuff 12. Thewrinkle-free band 34 is formed in the region of the cuff 12 where thecuff diameter is substantially equal to the patient's trachea. Thewrinkle-free band 34 also includes a small part of the cuff 12 with cuffdiameters that are only slightly larger than the tracheal diameter, asthis part of the cuff does not include cuff diameters that are largeenough to support wrinkling or folding. As shown, the cuff walls aregenerally flush against the tracheal walls 28. As the tracheal walls 28may be slightly irregular, the wrinkle-free band may vary from patientto patient. Because of the irregular shape of the trachea and the factthat the tube may not be centered radially, the wrinkle-free band 34 mayhave varying width around its outer diameter as well as have its centervary axially as a function of angular position in the trachea. Forexample, the plane of the wrinkle-free band 34 may have varying angles,including angles 0-45 degrees off-axis from an axis orthogonal to thepatient's trachea. The wrinkle-free band 34 may be characterized by itslength along the axis of the tube 16, or along the axis of the patient'strachea. In certain embodiments, the wrinkle-free band 34 provideswrinkle-free contact of least 1 mm along the patient's trachea. Inspecific embodiments, the wrinkle-free band ranges from 1 mm to 3 mm insize, or from 3 mm to 6 mm in size.

FIG. 6 depicts a top view of a cross-section through the region 36 ofthe tapered cuff 12 in which the cuff wall diameters are smaller thantracheal diameter. In this minimal contact region 36, the cuff walls aregenerally not in contact with the patient's tracheal walls, leaving agap 42 that increases in size as the cuff wall diameter decreases. Thisarrangement may provide additional advantages related to patientcomfort. As a substantial region of the tapered cuff does not contactthe trachea walls 28 during use, tracheal tissue irritation may beminimized.

It is also envisioned that a tapered cuff 12 as provided herein maytaper away from the distal end of the conduit 16, as shown in FIG. 7.Such an arrangement may provide similar advantages to the taper cuff 12that tapers towards the distal end of the conduit 16 as provided herein.In other embodiments the inflatable cuff 12 may assume a variety oftapered shapes when inflated. For example, referring now to FIGS. 8 and9, various exemplary cuff shapes are depicted. FIG. 8 depicts anexemplary cuff 43 having a generally hourglass shape, i.e., two taperedsections 41A and 41B generally connected at their apexes. Similarly,FIG. 9 depicts an exemplary cuff 45 with tapered sections 46A and 46Bthat is wider at the midsection 44 of the tapered sections 46 than atthe proximal end 48 or the distal end 47, i.e., two cones generallyconnected at their bases. It is envisioned that cuff 43 and cuff 45 mayprovide the advantage of providing dual wrinkle-free bands along thetracheal walls when inserted into a patient's trachea. The dual bandsmay provide improved sealing by providing greater total wrinkle-freecontact are with the tracheal walls. In certain embodiments, additionalcuff shapes that may form multiple wrinkle-free bands are alsocontemplated. As will be appreciated by those of ordinary skill in theart, other cuff shapes are within the scope of the present disclosure.

The tapered cuffs 12 as provided herein may include cuff walls 24 withconstant or varying wall thicknesses along the length of the taper. Cuffwall thickness may vary from the widest part of the taper to thenarrowest part of the taper. In certain embodiments, it is advantageousto specify cuff wall thickness variation because certain cuff wallthicknesses in the wrinkle-free band 34 may help to terminate the foldsthat are present in the wrinkled region 32 of the tapered cuff 12 (as inFIG. 3-FIG. 6). Thicker cuff walls tend to be less flexible than thinnercuff walls, and thus less likely to form wrinkles If the walls of thewrinkle-free band 34 are thicker than the walls of the wrinkled region32, the wall thickness may aid in the termination of the wrinklesCertain wall thicknesses may be associated with wrinkles that are moreeasily terminated by the “band” that forms at the point where the cuffdiameter matches the trachea. In certain embodiments, it is contemplatedthat at least a portion of the cuff walls in the tapered region of thecuff are less than 60 microns in thickness. In another embodiment, thecuff walls are between 10 microns and 3 millimeters in thickness. Incertain embodiments, the cuff walls are between 0.5 mils (where mils arethousandths of an inch) and 3 mils. In specific embodiments, the cuffwalls vary along the length of the taper from between 2 microns to 140microns in thickness, from between 20 microns to 60 microns inthickness, and from between 30 microns to 50 microns in thickness. Incertain embodiments, it may be advantageous to provide a cuff 12 with aconstant thickness,

This thickness specification may be accomplished in a number of ways.For example, in one embodiment, the tapered cuffs may be manufactured bya blow molding process or extrusion blow molding process. For example,the cuffs may also be made by using preextruded tubing and applying heatand pressure appropriately within a molding cavity to achieve thedesired shape (blow molding). These cuffs can also be formed byextrusion blowmolding, wherein an extruder fed polymer pellets melts thepolymer and feeds the molten polymer through a die to form a tube shape.This still molten polymer is then captured in a mold and air pressure isapplied to expand the tube out to the walls of the mold, thus achievingthe desired shape. In the extrusion blow molding process, a core ormandrel of the extruder has apertures to admit a gas such as pressurizedair or an inert gas like nitrogen, into the medical device in theneighborhood of the cuff. After a length of medical device has beenextruded, a mold clamps the medical device around the mandrel. As gas isadmitted to the cuff area through the mandrel, the cuff expands againstthe mold. In the alternative, the cuff wall may be expanded in a seconddiscrete expansion process following an extrusion or molding process,such as with a shuttle blow molding process. After initial extrusion,the extruded cuff will have a generally tubular shape with asubstantially uniform wall thickness. This tubular shape may then beblown into the tapered shape. This process results in the area of thecuff with larger diameters having thinner walls because the same amountof material is stretched over a larger area. In an alternate embodiment,the wall thickness, constant or variable, along the length of the tapermay be specified in the blow molding process by using a programmableparasin on the extruder. A programmable parasin allows the wallthickness being extruded to be controlled as a function of length.Therefore, the extruded section may have walls of varying thickness.This extruded section may then be blowmolded as described above. Othercuff shapes and designs are discussed in the U.S. patent applicationstitled “ENDOTRACHEAL CUFF AND TECHNIQUE FOR USING THE SAME” to Donald S.Nelson and Dhairya Mehta filed on Jun. 22, 2006, the U.S. patentapplication titled “ENDOTRACHEAL CUFF AND TECHNIQUE FOR USING THE SAME”to Seamus Maguire, Sean Morris, Paul O'Neill, and Patrick Joseph Tiernanfiled on Jun. 22, 2006, and the U.S. patent application titled “THINCUFF FOR USE WITH MEDICAL TUBING AND APPARATUS FOR MAKING THE SAME” toJoel Colburn and Roger Caluya filed on Jun. 22, 2006, which are herebyincorporated by reference in their entirety.

One example of such a suitable blow molding process 50 is depicted inthe flowchart of FIG. 10. In this example, a tube, such as an extrudedpolyurethane tube, is loaded (block 52) into a blowing machine or moldassembly with a tapered shape, such as a machine used to blowangioplasty balloons. As described above, the extruded tube may havewalls of varying thickness. Balloon blowing machines typically allowprocess parameters such as extrusion stretch, blow pressure, andtemperature to be controlled. Once loaded, the mold assembly is closed,and the tube is clamped at each end (block 54). The tube is stretchedand air is blown into the tube via an air conduit, such as an air hoseor nozzle, connected to a source of pressurized air, such as an air pumpor pre-pressurized source, to achieve a desired positive pressure withinthe tube (block 56). Heat is applied to the tube (block 58), such as viaheating elements integral to the mold assembly. As the heat is applied,the stretch of the tube is relaxed and the air pressure within the tubeis increased (block 60). Once the desired temperature is reached it ismaintained for an interval of time (block 62). Afterward, thetemperature of the mold assembly is allowed to drop or is activelycooled (block 64). A vacuum is applied within the tube, which nowincludes the blown cuff, to release the tube and cuff from the moldassembly and the tube and cuff are removed from the mold assembly (block66).

For example, in one particular implementation, a commercially availableextrusion of Dow Pellethane® 2363-90A having an inner diameter of0.239±0.005 inches (6.0706±0.127 mm) and a wall thickness of 0.008inches (0.2032 mm) may be blown to form a cuff 12 suitable for use witha 7.5 mm internal diameter (ID) endotracheal tube. The extruded tube maybe stretched 50 to 100 mm on each end and a pressure of 1.0 to 2.0 baris applied within the extruded tube. The extruded tube is heated for 50to 100 seconds. As the temperature ramps up, the stretched ends of theextruded tube are relaxed to 20 to 70 mm and the air pressure within theextruded tube is increased to 1.5 to 2.1 bar. The temperature is allowedto increase to 120 to 150° C., where it is maintained for 10 to 30seconds. The mold assembly is then cooled to 40 to 55° C., a vacuum isapplied to the molded extrusion and cuff, and the extrusion and cuff areremoved from the mold assembly. In another embodiment, the cuff wallthickness may be controlled by a dip coating process (not shown). Forexample, by controlling the withdrawal rate of a cuff mandrel from a dipcoating solution, the wall thickness can be controlled. Using thiscontrol or multiple dips, it is possible to obtain even step functionchanges in wall thickness.

In certain embodiments, it may be desirable for the tapered cuff toinclude an antimicrobial surface to prevent the adhesion and propagationof biofilms. As shown in FIG. 11, a wall 24 of a cuff 12 may be ahydrophobic polymer with an outer antimicrobial layer 78 that includes ahydrophilic polymer and an antimicrobial compound disposed on an outersurface 80 of the cuff wall 24. The antimicrobial layer may include anantimicrobial metal, such as copper, silver, or gold. In severalexemplary embodiments, the metal may be elemental silver, powderedsilver, silver ions (Ag⁻), or a silver bearing material like silveroxide (AgO). The hydrophilic layer may thus be an antimicrobial (AM)layer. In this way the colonization-inhibiting properties of thehydrophilic surface can be reinforced by anti-microbial properties.

It may be desirable for the metal to be released over time, while themedical device is in use. In one embodiment, therefore, a silver-bearingtime-release material may be a phosphorus-based glass material thatdissolves in water at a rate that may be a function of its particularformulation. The glass may also contain trace amounts of other elements,such as calcium oxide (CaO). The rate at which silver is released mayfurther be a function of the rate at which the phosphorus-based glassmaterial dissolves in water. The silver, or the phosphorus-based glassmaterial, or both, may be powdered. The release of silver over time,which is defined as the elution rate and is measured inmicrograms/cm²/day, may thus be tailored to the specific needs of theapplication by specifying the formulation of the phosphorus-based glassmaterial, such as the material described in U.S. Pat. No. 6,143,318. Inone embodiment, the silver bearing material may be made up of about5-10% by weight, e.g. about 7.5% phosphorus-based glass by weight. Sucha material is available from Giltech Limited, 12 North HarbourIndustrial Estate, Ayr, Scotland, Great Britain KA8 8BN. In oneembodiment, the elution rate should be up to about 0.01micrograms/cm²/day. In another embodiment, the elution rate may bebetween about 0.01 and 1.0 micrograms/cm²/day. In another embodiment,the elution rate may be about 0.4 micrograms/cm²/day.

In other embodiments, bioactive pharmaceutical agents such as abronchodilator, an anti-inflammatory agent, or a local anesthetic, maybe substantially dispersed in a phosphorus-based glass material within ahydrophilic layer. Such bioactive pharmaceutical agents may be deliveredto and absorbed by adjacent tissues in substantially the same manner assilver. Regulation and control of dosage, elution rate, and thickness,in substantially the same manner as silver, may also provide abeneficial pharmacologic or therapeutic action.

A hydrophilic coating may be applied to the surface of a medical deviceby, e.g., extruding, molding, dipping, spraying, washing, or paintingthe hydrophilic coating on the surface. In one embodiment, a medicaldevice may be formed by extruding a wall of hydrophobic material alongwith one or more layers of an antimicrobial material. In anotherembodiment, a medical device may be formed by molding a wall ofhydrophobic material along with one or more layers of an antimicrobialmaterial. The antimicrobial layer may be formed on an inner or an outersurface of the medical device wall. The antimicrobial layer may becomprised of, e.g., polyurethane, such as a medical grade hydrophilicthermoplastic polyurethane into which has been substantially dispersed asilver-bearing phosphorus-based glass material. In one embodiment, theantimicrobial layer may be within a range of about 0.002 mm-2.5 mm inthickness, or about 0.13 mm in thickness. In another embodiment, theantimicrobial layer may be within a range of about 0.002 mm-2.5 mm inthickness. In another embodiment, the antimicrobial layer may be up toabout 6.35 mm in thickness. In another embodiment, the hydrophobicpolymer, hydrophilic polymer and the antimicrobial compound may becompounded together and extruded to form a cuff wall 24.

The tracheal cuffs of the present techniques may be incorporated intosystems that facilitate positive pressure ventilation of a patient, suchas a ventilator. Such systems may typically include connective tubing, agas source, a monitor, and/or a controller. The controller may be adigital controller, a computer, an electromechanical programmablecontroller, or any other control system.

Typically, endotracheal cuffs are inflated within a patient's tracheasuch that the intra cuff pressure is approximately 20-25 cm H₂O.Endotracheal cuffs utilizing inflation pressures significantly greater25 cm H₂O may be referred to as high-pressure cuffs, while cuffs thatare able to effectively seal the trachea at pressures less than 30 cmH₂O may be considered low-pressure cuffs. In certain embodiments, intracuff inflation pressures of 10-30 cm H₂O may be used with the taperedcuffs of the present techniques.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

What is claimed is:
 1. An inflatable balloon cuff comprising: a proximalopening and a distal opening in a wall of the balloon cuff; and atapered section along at least 50% of the length along an axis of theinflated balloon cuff, wherein at least a portion of the tapered sectionis configured to form a seal against a tracheal wall of a patient,wherein the tapered section comprises a balloon wall with continuouslyvarying thickness along the tapered section, and wherein the taperedsection comprises: a sealing portion, wherein the sealing portion isadapted to form a wrinkle-free band at least 1 millimeter in lengthagainst a patient's tracheal wall when inflated; a wrinkled portion,wherein a largest diameter of the wrinkled portion is larger than atracheal diameter such that the wrinkled portion forms a wrinkled bandagainst a patient's tracheal wall when inflated and wherein the wrinkledband is longer than the wrinkle-free band; and wherein the wrinkle-freeband has a first balloon wall thickness greater than a second balloonwall thickness in the wrinkled portion.
 2. The balloon cuff of claim 1,wherein the tapered section comprises a substantially constant taperrate along the length of the tapered section.
 3. The balloon cuff ofclaim 1, wherein a taper angle of the tapered section is between 9 and20 degrees.
 4. The balloon cuff of claim 3, wherein the taper angle isat least 11 degrees.
 5. The balloon cuff of claim 1, wherein the ballooncuff comprises polyethylene teraphthalate (PETP), low-densitypolyethylene (LDPE), polyvinyl chloride (PVC), silicone, neoprene,polyisoprene, polypropylene, or polyurethane (PU).
 6. The balloon cuffof claim 1, comprising a tracheal tube coupled to the balloon cuff,wherein the tracheal tube passes through the proximal and distalopenings in the wall of the balloon cuff.
 7. The balloon cuff of claim6, wherein the tapered section tapers towards a distal end of thetracheal tube or a proximal end of the tracheal tube.
 8. The ballooncuff of claim 6, wherein the tracheal tube is operatively connected to aventilator.
 9. An inflatable balloon cuff comprising: a proximal openingand a distal opening in a wall of the balloon cuff and a tapered sectionalong an axis of the inflated balloon cuff comprising a widest diametercloser to the proximal opening than the distal opening, wherein at leasta portion of the tapered section is configured to form a seal against atracheal wall of a patient and wherein the tapered section comprises aballoon wall with continuously varying thickness along the taperedsection and wherein the tapered section comprises: a sealing portion,wherein the sealing portion is adapted to form a wrinkle-free band atleast 1 millimeter in length against a patient's tracheal wall wheninflated; a wrinkled portion, wherein a largest diameter of the wrinkledportion is larger than a tracheal diameter such that the wrinkledportion forms a wrinkled band against a patient's tracheal wall wheninflated and wherein the wrinkled band is longer than the wrinkle-freeband; and wherein the widest diameter of the inflatable balloon cuff,when inflated outside the patient, is located within the wrinkledportion when the inflatable balloon cuff is inside the patient andcomprises a smallest balloon wall thickness of the inflatable ballooncuff such that at least part of the wrinkled band is thinner than thewrinkle-free band.
 10. The balloon cuff of claim 9, wherein the taperedsection comprises a substantially constant taper rate along the lengthof the tapered section.
 11. The balloon cuff of claim 9, wherein a taperangle of the tapered section is between 9 and 20 degrees.
 12. Theballoon cuff of claim 11, wherein the taper angle is at least 11degrees.
 13. The balloon cuff of claim 9, wherein the balloon cuffcomprises polyethylene teraphthalate (PETP), low-density polyethylene(LDPE), polyvinyl chloride (PVC), silicone, neoprene, polyisoprene,polypropylene, or polyurethane (PU).
 14. The balloon cuff of claim 9,comprising a tracheal tube coupled to the balloon cuff, wherein thetracheal tube passes through the proximal and distal openings in thewall of the balloon cuff.
 15. The balloon cuff of claim 14, wherein thetapered section tapers towards a distal end of the tracheal tube or aproximal end of the tracheal tube.
 16. The balloon cuff of claim 14,wherein the tracheal tube is operatively connected to a ventilator. 17.The balloon cuff of claim 9, comprising a proximal portion connectingthe widest diameter to the proximal opening, wherein the proximalportion tapers from the widest diameter to a smaller diameter of theproximal opening.
 18. The balloon cuff of claim 17, wherein the proximalportion comprises balloon walls that are thicker than at least a portionof the wrinkled band.
 19. The balloon cuff of claim 9, wherein thetapered section comprises a minimal contact region comprising a smallerdiameter than the sealing portion, wherein the balloon walls in theminimal contact region are thicker than the balloon walls in the sealingportion.
 20. The balloon cuff of claim 9, wherein the balloon walls ofthe tapered section are between 1.75 inches and 0.15 inches when theballoon cuff is fully inflated.